The invention relates to a wound dressing comprising (1) a lower layer of a hydrogel of a polymer cross-linked under the influence of electron beam (E.B.) radiation, to which optionally one or more medicinal and/or antibacterial agents and/or one or more auxiliary substances have been added, and (2) a polymeric top layer A wound dressing is to be understood to mean herein not only a cover of a wound, but also a cover of an undamaged skin, for example, when protection hereof is desired from medical or cosmetic considerations.
Such a wound dressing is known from the literature, for example, from European Patent Application 305770 and from U.S. Pat. No. 4,646,730. In these patent publications a cross-linked polyvinyl pyrrolidone (PVP) gel prepared by exposing a PVP solution in water to E.B.-radiation is used as a lower layer to be provided directly on the wound. Various medicaments, for example, silver sulfadiazine, a known antibacterial agent, may be added to the said lower layer. In the United States Patent Specification mentioned hereinbefore it is suggested to add a stabiliser to the dispersion of silver sulfadiazine in the aqueous PVP solution so as to obtain in the E.B. radiation a gel having a uniform colour. The resulting hydrogel is provided on a suitable carrier, for example, a non-woven and/or a polyethylene sheet. Such a polymeric top layer is necessary to support the lower layer. However, polyethylene is not a suitable material to serve as a top layer for wound dressing because it is not or hardly permeable to gas and vapour. As a matter of fact, the following requirements must be imposed upon polymeric sheet materials for wound dressing: (1) they must constitute a barrier to penetrating microor ganisms, (2) they must ensure a sufficient exchange of O.sub.2 and CO.sub.2 to stimulate the healing process, and (3) they must be sufficiently permeable to moisture vapour.
Suitable polymer sheet materials for wound dressing are described in European Patent Application 11471. Such materials are manufactured, for example, from polyether-polyurethane copolymer and have a sufficient elasticity to adapt to the skin in the form of a sheet or film. Moreover, such materials are particularly suitable for wound dressing because they combine a good moisture vapour permeability with the property of barring microorganisms. The polymer sheet to be used as a wound dressing in the last-mentioned European Patent Application comprises on one side an adhesive layer in which an antibacterial agent, for example, silver sulfadiazine, may be incorporated.